3 Replies Latest reply on Aug 13, 2008 1:24 PM by Sara Stults

    Applying non-linear forces

    Brendan L
      Hi everyone,
      I am trying to run a COSMOSWorks static stress analysis of an aircraft wing with an elliptical lift distribution (greater lift near the root of the wing, and less at the tip). My lift distribution is defined by a 2-D curve, so I am applying the load at the aerodynamic center of the wing (approximately at the quarter-chord), rather than over the entire top surface.

      I have created a split line at the quarter chord to split the top surface of the wing, and I am trying to apply my force along the line, but COSMOS does not allow me to use an equation to define the force if it is applied on an edge or line.

      Do you know if there is a better way to apply the force so it realistically models the elliptical distribution? Would it be better to apply the load over the top surface of the wing so that it can vary with the equation or to apply different forces to points along the line?

      I am new to COSMOS, and am using COSMOSWorks Advanced Professional 2008 SP 0.


      Sara Stults
        • Applying non-linear forces
          Steven Dinsdale
          Personally, I would apply the lift over the whole surface. If the solution takes too long you could try the point method but I don't think that will give you the same results. I would recommend re-running it with 2-3X the number of points until the solution converges and along many lines.

          • Applying non-linear forces
            Bill McEachern
            You could add another split line so you get a surface that approximates the "line" (ie a narrow surface. Otherwise you could put a linear distribution in the free stream direction along with the elliptical one in the transverse tot he free stream which is what is typically done. The non-linear load distribution has this capability. You can check it by comparing he root loads or stresses with a point load approximation.
              • Applying non-linear forces
                Sara Stults
                Thanks everyone! (I'm the original poster, I used my coworker's account to post my question by mistake.)

                I ended up using several point loads along the line to approximate it for now, and I'm going to try modifying my equation to use 3-D data instead of 2-D data so I can apply it over the entire surface as a pressure load instead of a force. Hopefully this will be more accurate and I won't get stress concentrations around the force points.

                Thanks for the advice, it really helped!

                Sara Stults